The present invention relates to cementing operations and, more particularly, in certain embodiments, to plug-and-abandon operations using plugging compositions comprising cement kiln dust (“CKD”), pumicite, and/or lime.
In cementing methods, such as well construction and remedial cementing, sealant compositions are commonly utilized. As used herein, the term “sealant composition” refers to a composition(s) that hydraulically sets or otherwise develops compressive strength suitable for use in subterranean applications. One type of a sealant composition is a plugging composition that can be used in plug-and-abandon operations whereby a plug is formed in a well bore to seal off the well bore for abandonment. In performing plug-and-abandon operations, a plugging composition may be placed in the well bore at a desired depth. The plugging composition should set in the wellbore, forming a hardened mass (e.g., a plug) that seals of selected intervals of the well bore. The plug should prevent and/or reduce zonal communication and migration of fluids that may contaminate water-containing formations. It may desirable in certain instances to form one or more plugs in the well bore adjacent to hydrocarbon-producing formations and water-containing formations.
Sealant compositions used heretofore may comprise Portland cement. Portland cement generally is a major component of the cost for the sealant compositions. To reduce the cost of such sealant compositions, other components may be included in the sealant composition to replace some of the Portland cement. Such components may include cement kiln dust (“CKD”), fly ash, slag cement, shale, metakaolin, zeolite, and the like. CKD is a partially calcined kiln feed which is removed from the gas stream and collected, for example, in a dust collector during the manufacture of cement. The term “CKD” is used herein to mean cement kiln dust made as described above and equivalent forms of cement kiln dust made in other ways.